Motor Controller using transistors

In this circuit power supply is given by Pressing switch Sw(1).when we press the Sw(1) it shorts the N/O contact of relay RL(1) which gives the supply to our
circuit.The current which passing thorough resistor R8 gives the base current to transistor T5.Where the transistor T2 and T3 are making darlington pair.
A darlington pair has various applications associated with it and one of them is to use it as a switch. As the transistor's collector current is proportionally
limited by its base current, it can be used as a current-controlled switch.And transistor T4 ON when over or under voltage is given to transistor T3.

Where capacitor C2 is used for avoiding noise.where capacitor C2 with resistor R10 making a low pass filter which also gives us sufficient time delay.
There is a resistor network(VR1,R11,R12) which is used as a current sensor.Where zener diode ZD1 and ZD2 are used for the over voltage protection.
where capacitor C1 used as a noise filter of switching circuit and Diode D3 as rectifier.Relay RL(1) is DPDT(double pole double through) relay using for switching
with Sw(1) and Sw(2).

Circuit Diagram :

PARTS LIST

Resistors

R1 = 150 KΩ
R2 = 33 KΩ
R3 = 6.7 KΩ
R4 = 100 KΩ
R5 = 39 KΩ
R6 = 15 KΩ
R7 = 10 KΩ
R8 = 4.7 KΩ
R9 = 75 Ω/1W
R10, R13 = 47 KΩ
R11 = 470 Ω
R12 = 0.5 Ω
VR1 = 2.2 KΩ

Capacitors

C1 = 1000 µF/25V
C2, C3 = 47 µF/10V

Transistors

T1, T2, T3, T4 = BC148
T5 = SL100

Diodes

D1, D2, D3 = 1N4001
ZD1, ZD2 = 3.1V
ZD3 = 9.1V

Miscellaneous

SW1, SW2 = Push to on switch
X1 = 230 primary AC primary to 18-0-18, 500mA secondary transformer
OR
(110 primary AC primary to 18-0-18, 500mA secondary transformer)
RL1 = 12V, 200 Ω Double pole double throw

M = Motor

Circuit From : http://www.expertcircuits.blogspot.com/

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